In order to etch copper (Cu) widely used as a wiring material for a semiconductor device, a halogen gas, a halogen compound gas or a gas containing an ammonia (NH3) gas or a nitrogen (N2) gas in addition to the halogen gas or the halogen compound gas have been used as a processing gas in a high temperature environment. Since, however, the halogen gas or the halogen compound gas generates strong acid, components of a substrate processing apparatus easily corrodes in the high temperature environment.
In view of this problem, there has been proposed a method for etching a wiring or a layer made of copper (hereinafter, referred to as a “copper member”) by plasma without using a halogen gas as a processing gas (see, for example, Non-Patent Document 1). In this method, only a hydrogen gas is used as a processing gas, and a vacuum ultraviolet ray having a wavelength of about 100 nm is generated when the hydrogen plasma is generated. Further, a chemical reaction between hydrogen plasma and copper is facilitated by irradiation of the vacuum ultraviolet ray. As a result, a compound of copper and hydrogen is generated. Then, copper is etched by vaporizing the compound of hydrogen and copper.    Non-Patent Document 1: Fangyu Wu, Galit Levitin, and Dennis W. Hess, “Low-Temperature Etching of Cu by Hydrogen-Based Plasmas”, ACS APPLIED MATERIALS INTERFACES, VOL. 2, No. 8, 2175-2179, 2010, published on Jul. 16, 2010
In the above method, however, an etching rate of the copper member is low and, thus, the method has been considered to be lack of practicality.